Hypernatremia is defined as a serum sodium greater than which value?

• A. 130 mmol/L
• B. 140 mmol/L
• C. 150 mmol/L
• D. 160 mmol/L

Answer: (C)

Hypernatremia means the serum sodium is higher than the normal range. In newborns and adults, the typical upper limit of normal is about 145 mEq/L. Among the options, 150 mmol/L is the value that places the patient into the hypernatremic range, since 130 and 140 are within or below normal and 160, while also hypernatremic, represents a higher level. So 150 is the threshold that best reflects the onset of hypernatremia given the choices provided. In clinical terms, hypernatremia often points to dehydration or excess sodium relative to water, and careful, gradual correction is important to avoid shifts that could harm the brain.